The present invention relates to a timer device for controlling the ON/OFF of a power source and, more particularly, to a timer device which returns to an initial state when a power source is turned off and then turned on at a short interval. In the initial state, the device prevents equipment incorporating it from being used illicitly or against rules for a long period of time.
A timer device for the ON/OFF control of a power sources is extensively used in various ways in the modern society. The timer device allows, for example, a video cassette recorder to be automatically switched on at a designated time for starting on a recording operation. Also, the timer device is capable of switching on equipment only for a designated period of time and then switching it off automatically. This kind of timer device can be readily implemented by the combination of a timepiece circuit and a power source control circuit.
However, the conventional timer device cannot serve the expected function for some applications. For example, assume the timer device built in a television/video set usually installed in a hotel room. With the television/video set, the viewer is usually not charged for ordinary TV programs, but charged for special programs including latest movies. The timer device is used to televise a movie free of charge only for a preselected period of time, thereby allowing the viewer to decide whether to see the movie. The problem is that when the power source of the timer device is turned off, the preselected period of time for free television is initialized. The viewer, therefore, can see the pay movie without being charged by turning on and turning off the power source of the timer device repeatedly.
Japanese Patent Laid-Open Publication No. 61-7911 discloses a timer device capable of preventing a power source from being turned on for a predetermined period of time after it has been turned off. However, this timer device is so arranged as to obviate a rush current when a power source is turned off and then turned on at a short interval. This kind of function is different from the originally expected function stated above.